Paving block and process of making the



UNITED STATES JAMES S. DOWNARD, OF ARDMORE, OKLAHOMA.

PAVING Bnocx .AND rnoonss or mum rnn snnn.

No Drawing.

To all whom it may concern:

Be it known that I, J AMns'S. DOWNARD, a citizen of the-United- States,and a resident of Ardmore, in the county of Carter and State ofOklahoma, have invented certain new and useful Improvements in PavingBlocks and Processes of Making the Same, of which the following is aspecification.

My invention relates to paving blocks and the process of making thesame, and particularly to a block used as a wearing surface upon asuitable base or as a pavement without a base other than the block orsheet itself Which is manufactured from natural asphalt rock orcombinations of other mineral aggregates in combination with asphaltrock,

It has been hitherto proposed to form asphalt paving blocks from amixture of particles of stone compounded with sand and asphalt'as minedis broken into pieces of provide a mixed with asphaltum after heating,the asphaltum cementing the particles together and coating them, whichrecess is carried on under high pressure. This process is defective inthat, while 10% to 11% is the eflicient percentage of bitumen in apaving mixture, it produces a mixture which rarely exceeds 5% for thereason that if it is rich in bitumen, the blocks lose their originalform when subjected to the heat'of the suns rays, and cannot be storedbecause they. crack, break down or lose form. Manufacturers haveendeavored'to avoid these difficulties by reducing the amount ofcementing asphalt and by making the blocks, under great pressure, but itis obvious that the resulting material is too brittle becauseflofdeficient bitumen.

It is a purpose of my invention to overcome those difficulties and toproduce blocks which can be stored, shipped and used without losingtheir form or integrity under ordinary climatic conditions by providinga process of forming blocks which permits the use of 10% or more ofbitumen in each block.

It is also a. purpose of my invention to rocess of'making blocks whichallows bloc s to be manufactured under ordinary pressure' by simplymolding the material and to contain any percentage of asphalt desired. II

In carrying out my invention, natural rock predetermin sizes dependingupon the thickness gs; e ultimate block and the parclimatic conditions.

Specification of Letters Patent. Patented Jan. 31, 1922. Applicationfiled September 30, 1919. I Serial No. 527,432.

ticular use to which it is :to be adapted. These particles of asphaltare carefully selected so that they will fit closely together and thusreduce the voids in the mineral ag regate to the least possible amount.

mastic is' now prepared byfenriching rock asphalt powder with purebitumen (asphalt) until it is plastic or mastic. The pure itumen must beof a high melting point so that the temper of the mastic is not affectedby exposure to the sun when the surrounding air shows a temperature ofFahrenheit. To secure such a mixture there is added to the mastic anyasphalt or.asphaltite that will raise the melting point such asgilsonite, imponsite, grahamite, mineral rubber, or blown asphalt.

voids between the particles of natural asphalt rock as assembled, theentire mass be ing thoroughl mixed in a suitable mixture" and finally deivered=,to the moulds where it is moulded into blocks of the desiredsize. The finished blocks are subsequently cooled with water, after.which they are stacked in storage for future use.

The resulting block or sheet, depending upon the particular use of thematerial, is substantially a natural rock asphalt pave ment composed ofparticles of natural ashalt arranged to reduce the voids and oinedtogether with a mastic to form a homogeneous mass which rovides forexpansion and contractiomehminates the possibility of cracks, andinsures the block retaining its original form under ordinary It isnecessary that the natural rock as halt constitute a major portion ofeach bloc or sheet, in other words, each block or sheet must contain 51%or more of the rock'asphalt so that it essentially consists of asphaltin its natural state.

Although I have herein described only one understood that variouschanges may be made in the various ingredients and steps in the processwithout departing from the spirit of the invention- .and the spirit andscripe of the appended claims. a

claim! 1. A process of mak ng. pavingblocks which consists indisintegrating natural asaving thus describedmyf invention, 1"

' phalt rock into; fragments, arranging the particles to mduce the maidst0 the p05- sible amoun.t,'mixiz1g the same with a mag- :i-c, andfinaflymoidingtha mass into blacks, 2. A pmcess of making paving; blmkiswhich consists in arrangizag fine fI'gQIQEIfiS 0f natural as me vcidsits the least 3; @sibie Bumbag :c r bssquen J @ssling 531% block A"paving 1010-211: comprising particles 0:? a1 asphalt reek anangeflr-Bduce JJ-hE u be: 0; voi to a mini

